Selection of p53-Deficient Stromal Cells in the Tumor Microenvironment

The tumor microenvironment is considered pro-oncogenic for reasons that, among others, involve the stimulation of cancer cell growth. However, little is known regarding how the tumor microenvironment affects the proliferation of stromal cells that coexist with cancer cells in the tumors. In the present study, we show that cancer cells trigger a paracrine response in normal fibroblasts that is not consistently mitogenic but may also become antimitogenic, inhibiting fibroblasts' proliferation in vitro. In vivo experiments on xenografts of MDA-MB-231 breast and A549 lung cancer cells in SCID mice or primary Notch-induced breast cancers that develop in transgenic mice showed that stromal cells frequently undergo senescence, confirming the presence of stress-inducing conditions within the tumor's microenvironment. These antimitogenic responses of the stromal cells were less pronounced in fibroblasts that are p53-deficient, suggesting that p53 plays a role in the execution of these mitogenic stress responses. In addition, they provide a biological basis for the selection of certain stromal cell subpopulations within malignant tumors exemplified by the p53-deficient stromal cells. Indeed, reconstitution of A549 human lung tumors in mice with admixed wild-type and p53-deficient stromal fibroblasts indicates that the selection of p53-deficient stromal cells is more intense when the number of cancer cells, and therefore the intensity of the stress response-inducing signals, is higher. These findings possess implications related to the effects of the cancer cells in the stromal cells and provide hints for the mechanism(s) underlining the transition of the normal stroma to cancer-associated stroma.

TGF-β1, Smad-2/-3, Smad-1/-5/-8, and Smad-4 signaling factors are expressed in ameloblastomas, adenomatoid odontogenic tumors, and calcifying cystic odontogenic tumors: an immunohistochemical study

OBJECTIVES

The TGF-β/Smad signaling pathway regulates diverse cellular functions, including tooth development, and is involved in numerous pathological processes such as tumorigenesis. The aim of this study was to investigate the immunoexpression of the TGF-β/Smad signaling pathway members in ameloblastoma (AM), calcifying cystic odontogenic tumor (CCOT), and adenomatoid odontogenic tumor (AOT).

MATERIALS AND METHODS

This retrospective cross-sectional study included 65 tissue specimens: 34 AMs, 13 CCOTs, and 18 AOTs. Serial sections were immunohistochemically stained with TGF-β1, Smad-4, Smad-1/-5/-8, and Smad-2/-3 antibodies, and a semiquantitative measurement of the positive cells was carried out by two oral pathologists using a 0-3 scale (0: no immunoreactivity, 1: <20% positive cells, 2: 20-50% positive cells, 3: >50% positive cells).

RESULTS

All biomarkers studied were found significantly decreased in AM compared to CCOT and AOT. AOT and CCOT expressed Smad-1/-5/-8 more strongly compared to AM (OR = 11.66, P < 0.001 and OR = 5.34, P = 0.013, respectively), and Smad-2/-3 immunostaining was found significantly increased in CCOT (OR = 10.42, P = 0.001) and AOT (OR = 5.16, P < 0.004) compared to AM. Similarly, Smad-4 was expressed more strongly in AOT and CCOT compared to AM (P = 0.001), while AOT demonstrated a fivefold higher chance to express TGF-β1 compared to AM (P = 0.011).

CONCLUSION

TGF-β/Smad signaling pathway is activated in AM, AOT, and CCOT. The statistically significant reduced TGF-β1/Smad immunoexpression in AM compared to AOT/CCOT could be associated with the more aggressive biological behavior of AM including increased cell proliferation and reduced apoptosis and differentiation. Thus, the biomarkers TGF-β, Smad-4, Smad-1/-5/-8, and Smad-2/-3 could serve as supplementary diagnostic indices between odontogenic tumors of high and low neoplastic dynamics.

p21/waf1 and smooth-muscle actin α expression in stromal fibroblasts of oral cancers

Background: Concerted alterations between stromal fibroblasts and neoplastic cells underline the carcinogenic process. Activation of alpha-smooth muscle actin (SMA) expression, a cytoskeleton protein normally expressed only in myoepithelial cells, is considered a landmark for the activation of stromal fibroblasts with little however being known regarding the mechanism governing the expression of SMA in the stroma.

Methods: We have evaluated by immunohistochemistry the expression of SMA in the stroma of oral malignant and pre-malignant lesions, in association with the expression of p53 and p21 tumor suppressors that were shown previously to be deregulated and/or mutated in stromal fibroblasts of various cancers. The effects of p21 knockdown in SMA expression and cell migration and the mRNA levels of endogenous p21 in fibroblasts co-cultured with cancer cells were also assessed.

Results: We found that both p21 and SMA expression was elevated in the stroma, but not the epithelium, of malignant as compared to pre-malignant lesions. We also noted that the expression of both was positively correlated, implying that SMA expression may be regulated by p21. Consistently with this notion we found that siRNA-mediated p21 suppression resulted in the reduction of SMA levels and also inhibited cell migration.

Conclusion: Our results show that p21 deregulation is associated with the activation of stromal fibroblasts of oral cancers by a mechanism that involves the stimulation of SMA expression.

Expression of p21waf1/Cip1 in stromal fibroblasts of primary breast tumors

During carcinogenesis, stromal fibroblasts undergo certain changes in concert with their neoplastic neighbors, an interaction that progressively leads to a cancer-associated state. However, despite the increasing appreciation of the importance of stromal/tumor interactions in the progression of cancer, little is known about the factors responsible for regulating the crosstalk between stromal fibroblasts and neoplastic cells. Here we show that the stage of the disease in primary human breast lesions affects p21 expression in the fibroblasts. In stromal fibroblasts of benign fibroadenomas, p21 exhibits a periductal pattern of staining, which is abolished in malignant adenocarcinomas in which p21 immunopositivity exhibits a mosaic pattern that eventually is abolished in more aggressive types of the disease. In order to address the role of fibroblasts' p21 in tumorigenesis, we have reconstituted MCF7 human breast cancers in mice, with fibroblasts differing in the p21 status. These experiments showed that p21 deficiency in stromal fibroblasts accelerates tumor growth through cell non-autonomous mechanism(s). In addition, even a transient, siRNA-mediated p21 suppression in fibroblasts sufficiently stimulates MCF7 and MDA-MB-231 growth in vivo. We propose that p21 regulation is intimately linked with the ability of stromal cells to affect tumor growth.

P53 mutations in stromal fibroblasts sensitize tumors against chemotherapy

The efficacy of chemotherapy is usually viewed as the outcome of cancer-cell-autonomous processes while the contribution of stroma is being overseen. Here we show that p53 mutations in stromal fibroblasts, a genetic lesion that is detectable in primary breast, prostate and probably other cancers, while they accelerate tumorigenesis they also sensitize tumours against conventional chemotherapy by doxorubicin and cis-platinum. The mechanism by which p53 of stromal fibroblasts affects the response of a tumour against chemotherapy is likely to involve the induction of senescence in the fibroblasts which in turns results in the production of growth factors acting onto the cancer cells by paracrine mechanisms. Our findings identify stromal fibroblasts as important modulators of the efficacy of anticancer therapy.

Rituximab in the treatment of high responding inhibitors in severe haemophilia A

The development of antibodies to factor VIII (FVIII) in severely affected haemophilia A patients is a serious complication associated with increased morbidity and mortality. Bypassing agents are used to treat acute bleeding episodes; however, elimination of the inhibitors can only be achieved with immune tolerance therapy (ITT) in 60-80% of cases. High responding (HR) inhibitors are more likely to respond to ITT if the titre is decreased to <5 BU over time or in selected cases after the administration of immunosuppressive drugs, plasmapheresis or immunoabsorption, techniques difficult to apply in children. Anti-CD20 (rituximab), a monoclonal antibody, was given as an alternative treatment in two haemophilic children with HR inhibitors and impaired quality of life, due to recurrent haemarthrosis. Rituximab was given at the dose of 375 mg m(-2), once weekly for four consecutive weeks. Both patients showed a partial response to rituximab reducing the inhibitor titre to <5 BU, thus facilitating ITT initiation; however, only the older patient eradicated the inhibitor within 21 days after application of ITT. The second patient, despite depletion of B cells, did not respond to ITT. No long-term side effects have been observed in both patients for a follow-up period of 20 and 18 months respectively. In conclusion, rituximab appears to be an alternative effective therapy to rapidly reduce or eliminate the inhibitor in selected cases of severely affected haemophiliacs before further proceeding to ITT. However, the dose and appropriate schedule, as well as long-term side effects need further investigation.

Evidence for nonautonomous effect of p53 tumor suppressor in carcinogenesis

Prostate, breast, and probably other epithelial tumors harbor inactivating mutations in the p53 tumor suppressor gene in the stromal cells, implying the nonautonomous action of p53 in carcinogenesis. We have tested this hypothesis by evaluating the tumorigenicity of MCF7 human breast cancer cells in severe combined immunodeficient mice that differ in their p53 status. Our results showed that, indeed, p53 ablation in the hosts reduced the latency for the development of MCF7 tumors. Furthermore, we show that heterozygous hosts frequently undergo loss of heterozygosity at the p53 locus in the tumor stroma tissue by mechanism that resembles the inactivation of p53 in primary tumors. To evaluate the impact of p53 ablation in the stromal fibroblasts, in tumorigenesis, tumors were reconstituted in mice bearing wild-type p53 alleles, by mixing MCF7 cells with fibroblasts isolated from mutant or wild-type p53 mice. Our results suggest that tumors containing p53-deficient fibroblasts developed faster and were more aggressive than their counterparts with wild-type fibroblasts, although their neoplastic component, namely MCF7 mammary carcinoma cells, was identical in both cases. These data strongly support the notion for the operation of a nonautonomous mechanism for p53 action in primary tumors and provide a mechanistic association between p53 mutations in the stromal component of epithelial tumors and carcinogenesis.

Petrositis and cerebellar abscess complicating chronic otitis media

A 12-year-old girl with chronic otitis media complicated by petrositis and cerebellar abscess is presented. Early surgical intervention, in combination with broad-spectrum antibiotics, provided a good outcome. Life-threatening complications of otitis media, although rare, still occur in developed countries.

Campylobacter jejuni O:19 serotype-associated Guillain-Barré syndrome in a child: the first case reported from Greece

We present a case of Guillain-Barré syndrome (GBS) following Campylobacter jejuni HS serotype O:19 infection in a child. Antibodies against C. jejuni and autoantibodies to the peripheral nerve gangliosides GM1 were positive, a pattern correlating well with the existence of an inflammatory neuropathy like GBS. The patient shared the HLA-B35 and HLA-DR8 antigens, which have been found to be increased in GBS patients with previous C. jejuni infection. As this is the first diagnosed C. jejuni-associated GBS case reported from Greece, further clinical and epidemiologic investigations are warranted.